Three-dimension radio direction finder



March 16, 1948. K. G. JANSKY THREE-DIMENSION RADIO DIRECTION FINDER Filed Aug. 30, 1943 VPatented Mar. 16, 1948 Karl Silver, assignortol "1 Belli; Telephone.;j Laboratories, Incorporated,

Newlork, N; Y., a corporation of New York arrlictgnniigqsto, isiaserial N0. 5oo, 54 1 This invention relates to radio direction nders and particularly to'absolute or threedimension direction finders.

As is known the azimuthal direction of arrival of a radio wave may be determined by a phasecomparison direction 'nder as,` for'exam'plafthe system disclos'ed'in the copending applicationfof H. T. Budenbom, Serial No. 741,372, iled August 23, 1934, now PatentNo."`2,4 23,437 issued Ju1y18, 1947 or by an amplitude-comparison direction iinder as, for example, the system disclosed in the copendingjoint application" of applicant and C. F. Edwards, Serial No. 431,194, filed February 17, 1942, now Patent No. 2,419,946 issued May 6, 1947. Also, as shown by'Patent2`,003,933 to J. W. Greig and British PatentV 504,293 to HMG. Thomas, arcanes .fhreeonensio;.syaemsxfor determining the actual or absolute Wavedirection, that is, the wave direction in both the vertical and horizontal planes, have been suggested. In general, the prior art absolute or three-dimension systems are based .0n-.the ainplitudefcom parison principle and are eiect 'acbmbiation of two distinct direction'nders, one'forth'eihorizontal plane and the other for the verticalplae. Moreover, most of the three-dimension 'systems heretofore proposed comprise complicated structures such as a rotating antenna or antenna arrays associated with separateindicators; and these complicated arrangements Varenotentirely satisfactory. In accordance with the' present in- It is still another object of this invention to secure simultaneous indications of the vertical and horizontal plane directions ofa radio wave on an indicator associated with-a simple antenna system. i Y, Y Y Y In accordanceV with one inbodimentof the invention, a verticalgantenna element is positioned at each `corner of fa squareloraright angle isosceles triangle, the elements being hereafter referred to as W (west), E (eastifand S (south). f

The three elements constitute'"tw61perpendicularly related linear arrays of two elements each, `one element `being common.' to both :,arrays" and ilar function andonwhich:

the remaining two elements `being `the same. Separate" receivers are connectedV by lines Aof equal length "to the three elements. Considering each array and thecorrespon'ding receivers,1 a phase meterfcomprising'a phase indicator land an adjustable phase shifter is connected to the outputs of the tworeceivers and-ani adjustable Vpotentiometer a'ssociatedlwith' a'isourceof direct current'is connected or g'anged. to thephase' shifter so'that, uponadjus'tment'oi Vthe phaseshifter,

-the potentiometer setting is Valtered to agree with that of the phaseslfiifter.` The' two potentiometer voltages arei applied to, 'different 'pairsoi plates `of ai cathode tube indicator, and a so-called s pot trace for indicationl is obtained.`f

In operation, the phase" Shifters are adjusted .tosecure a zero indicator reading whereby, for each' array, adirect curentpotentiometer voltag'is' obtained which is representative ofthe phase relationv ofi the :two i' antenna currents. Each of theftwovoltages thuspobtane'd is a funcwtionlof the vertical angle of 'wav'earrivah and the amount of displacement orideflection of the cathode tube'spot indication from' its center position is a measurefof tlnevert'icalA arrival angle. Also, one voltage 'is a cosinefunction and the other voltage is a` sine function'oi the angle in a horizontal plane between "the wave 'f direction'and the axis 'of one array.`. V.'Ihe angle between theradial path extending from thelspot tracedito the center; position of the Vspot andarefe'rence line on thef tubescreen representing lthe` reference Varray axis isa measure A"of `the 'azimuthal arrival angle.

The*invention willA be more. fully" understood from a .perusal of 1th`effollowingspecication taken in conjunction with the drawing on which likereferencecharacters'.denotel'elements of sim- 1 is a schematic illustration mentoftheinvention;l ,i Figs.y 2 and 3 :are respectively horizontal and verticalplanezdiagrams 'usedin explaining ythe operationof the system of Fig. V1; and f 'I Fig`4isa plantview oan antenna system `.comprising the receivingantenha systemv of Fig.

of oneembodi- 1 and'in'addition a local transmitting antenna.

the "rference antenna. Also antennas TE and S fthe spacing's .betweenwtherommonelementjand 55 constitute oneaifrayandantennasnE yandfW con*- Numerals 'I denote phase meters each compris-vv radial displacement and the reference character a denotes the angle between this radius and the reference line 28, corresponding to the axis 2 of the E-W antenna array. As will now be explained, the radius or length 2l is directly proportional to the Vvertical plane wave arrival angle A and the angle a is equal to the horizontal plane wave arrival angle 9, so that indications of both the vertical and horizontal plane wave arrival ing an adjustable phase shifter 8 having a mov- 'e able arm 9, and a phase indicator I0, one meter f being included between the receivers E and W and the other` meter being connected betweenthe receivers E and S. Numeral I I denotes a battery and numeral I2 designates a resistance connectedV in shunt to the battery and having its mid-point connected to the ground 5. Numerals I3 designate adjustable potentiometers connected in shunt to battery II, each potentiometer I3 comprising a resistive winding I4 and a movable contactarm I5. As shown by the rod or connection I6 the movable arms 9 and I5 of one phase shifter 8 and one potentiometer I3 are connected together for unicontrol operation; and the movable arms il and I of the other phase shifter 8 and the other potentiometer I3 are similarly ganged. Numeral i'I denotes a cathode ray tubeindicator having two horizontal plates I8 and I9 for vertically reflecting the tube beam and two vertical plates 2O and 2l for horizontally deflect-.ing the beam. Plate I8 is connected by conductor 22 to the movable arm I5 of the potentiometer I3 associated with the array E-S and plate is connected to the movable arm .I5 of the potentiometer associated with the .array E-W. The plates I9 and 2i and the mid-points of the potentiometer windings I4 are connected to the ground 5.

In operation, Fig. 1, separate components of an incoming wave 2.3 making an angle G in the horizontal plane with the reference axis 2 ofV array E-W and an angle A in the vertical plane with a horizontal or azimuthal plane, are absorbed by antenna elements I and conveyed over lines lIl to the receivers 3. Numerals 24 and 25 denote, respectively, the horizontal and vertical plane directions of the incoming wave 23. See Figs. 2 and 3. Considering each of the arrays E-W and E-S, detected voltages are obtained in the outputs of the two associated receivers and theirv phase relation as shown by indicator I0, corresponds to the phase relation of the two absorbed components. The phase difference, if anyI is eliminated or compensated by adjusting .the arm 9 of `phase shifter 8 to secure a zero reading on indi,- cator ID. Since the potentiometer contact arm I5 and the phase .shifter contact arm 9 are .unicontrolled, a direct current potentiometer voltage having a polarity and an amplitude representative of the phase difference is obtained and this potential is applied to platel8 .or 20 rof tube I'l. lIn other words, the direct current potential impressed across plates I8 and I9 representsv the phase relation of the currents absorbed by an.- tenna elements S and E; andthe potential iinpressed across plates 20 and 2l represents the phaserelation of the components collected by elements W and E, the phase of the components lnteroepted by element E being considered the .reference phase.

The two potentials on the quadrature plates of tube I'I Vcause a Vdeflection or displacement .from

the center position of the cathode beam and pro.-

duce a spot trace 26. Numeral 21 denotes the directions are .simultaneously obtained on the single indicator I1. Preferably the screen of the cathode ray tube I'I contains calibrated markings .such as the radial .angle lines 30 and the concentric circles 3I Yfor easily evaluating the two indications obtained.' Referring to Figs. 2 and 3 the phase difference,

` I Ew, of the potentials established in the antenna elementsl E and W is given by the following equation:

:21rd cos @reos A PE- W where 1r=3,14 and is a constant,

d=spacing between elements E and W and between elements E and S, and is a constant,

A=operating wavelength and is a constant.

Similarly, the phase difference, ons, between the potentials established in elements E and S is:

615V7-S=21rcl smG cos A (2) In Fig. 3, Im-w and @as are represented, respectively, by lines 32 and 33, the constant 2 lr n A being disregarded. Hence the direct current potential, PE-w, obtained at the potentiometer I3 associated with the E and W elements may be expressed where 1c is a constant.

Similarly, for 4the E and S elements the potentiometer voltage Pa-s is:

a point or spot 26 on a circle, the radius of the circle having a length I Y derived as follows:

cosA Thus, since the 'radius is a function of the wavelength, is. and the antenna spacing', d, in order to determine the vertical angle of arrival, the equip- S ment must be calibrated for each Wavelength on which measurements are tc be made.

Now

sin 9 cos 9 =tan 9 Hence Thus, the radius or distance 21 is a measure of the vertical wave arrival angle A and the angle a is equal to the horizontal wave arrival angle 9.

Although the invention has been explained in connection with speciilc embodiments, it is to be understood that it is not to be limited to the apparatus described inasmuch as other apparatus may be successfully employed in practicing the invention.

What is claimed is:

1. A method of determining the absolute direction in space of a radio wave which 'comprises simultaneously receiving three electric components of said wave, simultaneously obtaining a voltage representing the phase relation of one pair of components and another voltage representing the phase relation of another ,pair of components, and obtaining from said voltages two simultaneous indi-cations representing the wave arrival angles in two perpendicularly related planes.

2. A method of determining the absolute direction of an incoming wave, utilizing a cathode tube indicator having two pair of quadrature plates, which comprises simultaneously receiving at three spaced locations in the azimuthal plane electric components of said wave, the phase relation of one pair and the phase relation of a different pair of the three received components being pro-- portional to different functions of the horizontal plane wave arrival angle and proportional to the same function of the vertical plane wave arrival angle, simultaneously obtaining a pair of voltages each representing a different one of said phase relations, and simultaneously applying said voltages each to a different pair of said plates.

3. A method of determining the vertical and horizontal plane arrival angles of a radio wave, utilizing three receiving antennas positioned in a horizontal plane at the corners of a right angle isosceles triangle and constituting two arrays of two elements each, and a cathode ray tube indicator having two pairs of deecting plates positioned quadrature, which comprises simultaneously receiving three similarly polarized electric components of said wave, simultaneously obtaining a pair of direct current voltages representing the phase relations of the components received by each array and applying each voltage to a different pair of said plates.

4. A three-dimension direction nding system comprising means for simultaneously receiving at least three distinct electric components of an incoming wave, means for obtaining a pair of voltages, one representing the phase relation of one pair and the other representing the phase relation of another pair of said components, and means for simultaneously obtaining from said voltages an indication of the arrival angle of said wave in a given plane and an indication of the wave arrival angle in a plane perpendicular to the mst-mentioned plane.

5. A three-dimension direction nding system comprising means for simultaneously receiving at least three distinct electric components of an incoming-Wave, means for ascertaining the phase relation of one pair of said components and the phase relation of another pair of said components, means controlled by the last-mentioned means for obtaining a pair of voltages, one representing the phase relation of one pair and the other representing the phase relation of another pair of said components, and means for simultaneously obtaining from said voltages indications of the Wave arrival angles in perpendicularly related planes of propagation.

6. In combination, three vertical linear receiving antennas positioned at three corners of a square, means for simultaneously obtaining two voltages, one voltage representing the phase relation of the wave components received by one pair of closely positioned antennas and the other representing the phase relation of the components received by theother pair of closely positioned antennas, a cathode ray tube indicator having quadrature plates, and means for simultaneously applying each voltage to a different pair of plates.

'7. In combination, three vertical linear receiving antennas positioned at three corners of a right angle isosceles triangle and constituting two perpendicularly related arrays, separate receivers simultaneously connected to said elements, a

cathode ray tube having two pairs of quadrature plates, means for ascertaining the phase relations of the two wave components received by the antennas in each array, said means comprising separate phase meters connected between the two receivers for each array, means for obtaining potentials corresponding to the two ascertained phase relations and impressing each potential on a different pair of said plates.

8. A combination in accordance with the preceding claim, each phase meter comprising a phase shifter and a phase indicator.

KARL G. JANSKY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,208,378 Luck July 16, 1940 2,282,630 Busignies May 5, 1942 2,284,475 Plebanski May 26, 1942 

